Rotary impact tool

ABSTRACT

Rotary impact tool with torque overload mechanism for stalling the tool automatically in either direction of its operation. The torque overload mechanism includes a normally-open valve for relieving back pressure behind a centrifugally movable hammer pin on the rotor. This valve closes automatically to stall the tool at a predetermined torque load.

United States Patent Earl G. Roggenburk 4120 Behrwald Ave., Cleveland. Ohio Jan. 13, 1969 Continuation-impart of Ser. No. 636,528, May 5, 1967.

Patented Jan. 19, 1971 lnventor Appl. No. Filed ROTARY IMPACT TOOL 18 Claims, 4 Drawing Figs.

US. Cl 172/935, 173/12 Int. Cl 1 v 825d 15/02 Field of Search 173/935, 93.6,93,169, 12

[56] References Cited UNITED STATES PATENTS 2,784,818 3/1957 Maurer 173/936 2,947,283 8/1960 Roggenburk.. 173/93.5X 3,181,672 5/1965 Swanson 173/93 3,318,390 5/1967 Hoza et al 173/935 3,323,395 6/1967 Burnett et al. 173/93X 3,406,762 10/1968 Kramer 173/12 Primary Examiner-David H. Brown Attorney-Ely, Gorlick & Flynn ABSTRACT: Rotary impact tool with torque overload mechanism for stalling the tool automatically in either direction of its operation. The torque overload mechanism includes a normally-open valve for relieving back pressure hehind a centrifugally movable hammer pin on the rotor. This valve closes automatically to stall the tool at a predetermined torque load.

ROTARY IMPACT Tool,

This application is a continuation-impart of my copending application, Scr. No. 636,528,filed May 5, 1967.

This invention relates toan air motor-operated rotary impact tool, such as an impact wrench. j v a A principal object of this invention is to provide a novel arrangement for automatically stalling a rotary impact tool,

preferably a tool as disclosed in. my. cop'ending application just referred to. whenever it encountersga torque overload condition.

Anotherobject-of this invention is to provide such-a stalling preferred embodiment thereof which is'illus'trated inthe ac-. companying'drawing.

' t In the drawingz FIG. I is a longitudinal sectional view of a rotary impact tool incorporating the improvements in acjcordance with the present invention;

A FIG'. 2 is a vertical cross section -taken along the line 2-2 in FIG. '1 ands'howing the venting mechanism in the end cap in its normal condition; I f f v.

' FIG, 3 is a fragmentary view similar toFlG. 2 and showing .the venting mechanisni closedto stall thetool when a torque overload occurs; and 1 front end of thejrotor an'd the hammer pin of the tool, taken I along the line in FIGQl, with the hammer pin engaging the I anvil to impart rotation from the rotor to the anvil, I

Because of the eccentric position of the,- innerliner'member l3'with respect to the rotational axis'of the rotor, the vane 16 which is in a vane slot lfacing downward toward the handle I 11 is almost fully retracted within this vane slot, whereas-the arrangement which has provision for. selectively determining a stem 28 connecting them. The lands havea'sealing fit with H6. 4 is a fragmentary vertical'crossjsection through the.

Referring first to FIG. ,I, theimpact tool'illustrated therein is identical, except for the overload release of thepresent invention, to the tool disclosed andclairned in my copending .U.S. Pat. application, Ser. No. 636,528, filed May 5 i967.

This tool has'a housing with an integral handle 11 to be held by the user and an end lcaplZ which is suitably attached toth'e housing proper. Immediately to the leftof the end-cap 12 the housing l ti definesa cylindrical recess 8 which snugly receives astationary two-piece liner, composed of an outer liner member 9 and a then cylindrical inner, liner member 13. The outer linermember 9 has a radial wall thicknesswhich varies progressively from a maximum at the bottom in FIG. 1 to a minimum at the top, so that the cylindrical inner liner member 13 is supported offcenter with respect to the housing recess 8.

The relatively massive rotor 14 of an air motor is mounted for rotation about an axis which coincides with that of the housing recess 8 and which, therefore, is eccentric with' respect to the inner liner member 13. This rotor has a pluralityally between the end cap l2 and the right end of the two-piece liner 9. 13 in FIG. 1. A ball bearing assembly 18 is engaged between the end plate "and the rotor 14 to support the latter for rotation with respect to the-nonrotating end plate 1.7, The right end of the rotor projects axially beyond the ball bearing :18 into a recess 19 in the housing end cap 12. Within this recess a nut 20 is screw threaded onto the end of the rotor, and a flat washer 21 is engaged between this nut and the inner race of the ball bearing 18.

At the rightend of each vane slot 15 inFlG. l. the rotor 14 presents a radial shoulder 22 which has a close running fit with the inner end face 17a of the end plate 17 andwith an annular washer 23 which abuts against the innerrace of the ball bearing 18.

diametrically opposite vane has the maximum clearance from the bottom of thevane slot in; which it is slidable. Between these two extremes. the rotor 14. vanes 16 and the inncrliner 13 together define suqcessiye motor-chambers of progressiv'ely increasing volume around the circumference of the rotor in both directions (clockwise and counterclockwise) from the lower end of the inner liner member [3 to its upper end. If pressurized air is introducedinto the grou'pof motor chambers which increase in volume progressively from bottom to top in a clockwise direction (viewed fromthe end plate 12) and air is discharged from the remaining group of motor chambers from 'top to bottom in this clockwise direction. then the rotor will be driven clockwisewhich is the "forward" direction. Converse-' ly, if pressurizedair is introduced into the group of motor chambers which increase progressively in volumefrom bottom'to top counterclockwise and air'is discharged from the remaining motor chambers in this counterclockwise direction.

the rotor'will be drivencountercloc'kwise, which is the "reverse" direction. I

A valve arrangement is provided onlthe tool for operation selectively by the user to cause the air motor to operate either 1 in the forward direction or in the reverse direction.

Referring to FIG. 1 at its lower end the outer liner member v 9 has a longitudinal bore 25 which slidably receives a directional valve constituted by a spool valve member presenting a pair of longitudinally'spaced cylindrical lands 26.27 and the bore 25. v

Liner member 9 has a "forward" motor port 29 intersecting the bore 25 and communicating with'a' groove 30 in the inner liner member 13 which extends up circumferentially clockwise from port 29 around app oximately at lower 'quadrant of the rotor 14. Groove 330 communicates directly with the space between the outside of the rotor 14 and the inside surface of the inner liner member 13 for almost half of the latters circumferential extent clockwise upward from its lower end to supply pressurized air to the corresponding motor chambers to produce forward rotation of the rotor.

Theouter liner member 9 also haslareve rse." motor port 31 leading to a groove 32in the inner liner member 13 which extends up circumferentially from port 31 counterclockwise around the opposite lower quadrant of ,the rotor 14. Groove 32 communicates directly, with the space between the periphery of the rotor 14 and the inside surface, of the inner 1 of radially, outwardly extending, circumferentially spaced vane slots 15 which slidably receive respective vanes 16. When the rotor rotates, the vanes 16 move radially outward liner member l3for almost the remaining half of the latters circumferential extent to supply pressurized air to the corresponding motor chambers to produce reverse rotation of the rotor.

Approximately midway a'xially between the two motor ports 29 and 31 the outer liner member 9 at its lower end has an air inlet port 33 which communicates with a longitudinal passage 34 in the body 10 through a port35 in the latter.

As shown in H6. 1, a coil spring 27' is engaged under compression between the spool valve and the end plate 17. This spring normally biases the spool valve to the FIG. 1 position,

in which the inlet port 33 is in communicatior with the for-' ward motor port 29, while the valve spool land 27 blocks the inlet port 33 from the reverse motor port 31.

The valve spool also has an intermediate position in which both motor ports 29 and'3l are closed by the respective valve spool lands 26 and 27.

Finally, the valve spool has a third position in which it is retracted to the right in FIG. 1 enough to connect the inlet port 33 to the reverse motor port 31, while the valve spool land 26 blocks the inlet port 33 from the forward motor port 29.

The left end of the spool valve is engaged by a pin 36. which is slidably disposed in a longitudinally extending opening 37 in the housing 10. This pin is attached to a reversing trigger member 38. This reversing trigger member carries a guide pin 39 extending parallel to and below the pin 36. The guide pin is slidably received in a bearing sleeve 40 carried by the housing 10. When the user grasps the reversing trigger member 38 with his index finger and retracts it fully to the right, the pin 36 forces the spool valve to the reverse position to which the inlet port 33 communicates with the reverse motor port 31.

The handle 11 of the tool has a vertical air inlet passage 41 which is screw-threaded at its lower end for connection to an air hose. A valve body 42 is mounted in the handle 11 at the upper end of this passage 41. This valve body has an external longitudinal groove 43 which leads from passage 41 into a recess 44 in the handle. The valve body 42 has a longitudinal passage 45 whose right end opens into the handle recess 44. The opposite end of passage 45 communicates with a vertical passage 46 leading into the longitudinal passage 34 in the body 10.

An on-off valve poppet 47 within the handle recess 44 is positioned opposite the right end of a longitudinally extending stem 48. The opposite end of stem 48 is attached to a main trigger member 49, which is disposed outside the handle 11 in the path of the lower end of the reversing trigger member 38 when the latter is retracted. A coil spring 50 normally biases the valve 47 to the position shown in FIG. 1, in which it closes the passage 45 in the valve body 42 to prevent the flow of pressurized air from the inlet passage 41 in the handle into the valve body passage 45.

When the user retracts the main trigger 49 against the urging of spring 50, the valve member 47 is unseated and pressurized air can flow through the passages 41 and 46 to the inlet port 35 for the spool valve. Unless the reversing trigger member 38 is also retracted at this time. the valve spool will be in its forward position, as shown in FIG. 1, and the air motor will operate in the forward direction.

To operate the air motor in reverse, the user may retract the reversing trigger 38. In moving to the right, the reversing trigger engages and retracts the main trigger 49 to open the inlet valve 47, as well as retracting the spool valve 26--28 to the reverse position in which the inlet port 33 is connected to the reverse motor port 31 for operation of the air motor in the reverse direction.

The inner liner member 13 has a primary exhaust port 51 at its upper end which registers with an exhaust passage 52 in the outer liner member 9 leading to openings in the body which pass the exhaust air to the exterior of the tool. The air trapped between successive vanes 16 on the rotor in the latters rotation from the motor port 29 or 31 up to the exhaust port 51 is passed out of the motor.

The outer liner member 9 has a pair of circumferential grooves 53, 54 in its periphery which communicates with the reverse motor port 31 when the spool valve is positioned for forward rotation of the motor. These grooves 53, 54 lead to openings in the housing 10 for exhausting air from between the vanes on the rotor in its return travel from the upper end of the liner down to its lower end.

Similarly. the outer liner member 9 has a second pair of peripheral grooves 55, 56 which communicate with the forward motor port 29 when the spool valve is positioned for reverse rotation of the motor. These grooves 55, 56 lead to openings in the housing 10 for exhausting air from between the vanes on the rotor in its return travel from the upper end of the liner down to its lower end.

The housing 10 of the tool has a cylindrical bore 60 extending forward (to the left in FIG. 1) from the chamber 8 where the air motor is located. The rotor 14 has an integral extension 14a which projects into this housing bore 60.

A massive annular end head 61 is press fitted onto the rotor extension 14:: to increase the effective mass of the rotor. The length of this end head 61 may be selectively varied so as to provide the total mass for the desired impact blow. as described hereinafter.

The right end face of the end head 61 on the rotor abuts against the left end of the outer and inner liner members 9 and 13 and is slidably engaged by the adjacent end faces of the vanes 16 in the air motor. The right end of the end head 61 overlies and provides a seal for the left end of each vane slot 15 in the rotor to minimize air leakage between the inlet and exhaust motor chambers in the air motor.

The periphery of the end head 61 on the rotor has a clearance in the housing bore 60, and pressurized air from the air motor can leak past the end head 61 into the interior of the housing to the left of the end head in FIG. I.

The rotor extension 1411 is supported for rotation by a ball bearing 62. comprising an outer race having a snug fit within the housing bore 60, an inner race on the rotor extension 14a, and balls engaged between these outer and inner races. The right end of the inner race of bearing 62, abuts against a snap ring 63 on the rotor extension 14a.

The rotor extension 14a terminates in a reduced from end 64. A rotatable anvil 65 presents a rearwardly-facing central recess 66 into which the front end 64 of the rotor extends. with rollers 67 engaged between them to support the rotor for rotation with respect to the anvil. These rollers insure that laterally directed load forces on the anvil will not interfere with the desired rotation of the rotor.

A ball bearing 68 is engaged between the outside of the anvil 65 and the front end of the housing bore 60. The outer race of this bearing 68 has a snug fit inside the housing bore and its front (left) end abuts against an integral front end wall 69 of the housing. A cylindrical spacer 70 is engaged axially between the outer races of the ball bearings 68 and 62. The inner race of bearing 68 is engaged axially between a snap ring 71 on the anvil and an integral annular flange 72 on the back end of the anvil. The periphery of flange 72 has a running fit inside the spacer 70, and the spacer preferably has a snug fit inside the housing bore 60. The anvil 65 has a reduced front end 73 projecting forward beyond the front end wall 69 of the housing for engagement with the tool (not shown) which is to be driven.

As best seen in FIG. 4 the anvil 65 has an integral arcuate extension 74 extending rearward from its flange 72 and having a running fit inside the cylindrical spacer 70. As shown, this extension 74 has an arcuate extent of more than 90.

The rotor extension 14a carries a radially movable hammer pin 75 for engagement with the anvil extension 74 to impart rotation from the rotor to the anvil 65 with an impact blow, as described hereinafter.

The rotor extension 14a has a radially extending recess 76 of circular cross section (FIG. 4) which slidably receives the inner end of the hammer pin 75. The rotor has a longitudinal passage 77 whose right end opens into a central recess 19 in the housing end cap 12. The opposite end of passage 77 opens into a small radial bore 78 which intersects the radially inward end of the recess 76 and into a slightly larger counterbore 79 which intersects the recess 76 radially outward beyond the longitudinal rotor passage 77. At the radially outward end of the counterbore 79 the rotor presents a shoulder 80 which terminates in an arcuate edge 81 that is part of the cylindrical wall of the recess 76. The hammer pin 75 when positioned radially outward, as shown in FIG. 1, has a cylindrical periphery which sealingly engages the sidewall of the recess 76 around its entire extent, including the arcuate edge 81. The hammer pin coacts with this edge surface 81 to provide a valve for relieving the air pressure which retracts the hammer pin at the completion of an impact blow on the anvil 65, as described hereinafter.

The hammer pin has a reduced outer end 82 of square cross section whose corners are at the cylindrical periphery of the inner end of the hammer pin. This outer end 82 of the hammer pin presents a flat edge surface 83 at its right side which abuts against the inner race of the ball bearing 62 in all positions of the hammer pin radially of the rotor.

The rotor extension 14a has a longitudinal groove in the bottom which passes air from the space between the end head 61 and bearing 62 into the space 84 which is bounded by the bearing 62, the flange 72 on the anvil and the spacer 70.

outward movement of the hammer pin.

- passage 77.'the central recess 19 in thefhousin'g end normally communicates with a passage to the atmosphere. as described hereinafter. Except'when a torque'overloa'd condition occurs,

as described hereinafter. every time the Ihanimer pin 75 'is retracted 'tadially'in'ward; air pressure in the space 84 is relieved to the atmosphere so as not to retard the next radially At its radially inward end. the hammer pin 75 has a central recess'86 which snugly receives 'a resilient bumper 87 of rubber orrubberlike material. This jbu'mper projects radially inward past the inner end of the hammer p'in'for engagement withthe inner end wall8 8 of the recess 76 in the rotor, when the hammerpin'is retracted radially inward. to cushion the latter ag'ainstsl'iock, i U h In the operation of this tool, the air motor is drivenby compressed air'and,--'when the rotor 14 reachsthe proper speed,

the hammer pin 75'Imoves radially outward under the influence of centrifugal force. As the'harn'mer pin revolves in unison-withthe rotor 14. it strikesonecircumferential'end of the anvil extension 74"(FIG. 4) a sharp blow, whose impact is enhanced by the heavy mass of the mom andthc heavy e'nd head 6Ldrivingthe anvil in the same rotationaldirection until the work load causes the air'motor to stall. at which time the rotor rebounds slightly. Atthis time the air pressure in'space '84 builds'upfto a value of several pounds per square -inch,ldue

' h to leakage from the air motorbetween-the vanes l6 and the endhead 6l .-around theend head-6l'and through the ball bearing'62 into space 84. Thisair pressure forces 'the hammer 1 pinradially inward until itclears'the anvil extension"74,'at 1 which time the rotor can resume. its rotation. When the hammer pin is thus retracted radially inward by air pressure it v mits the air pressure in chamber 84 to be exhausted to the atmosphere by way of the longitudinal rotor passage 77 and the chamber 19 in'fthe housing end .cap 12. The air expansion which takesfplace at this time cools the hammer pin 75 and the anvil extension 74. i I v r If air tool oil'or other suitablelubricant is introduced along with the pressurized air into the handle inlet passage 4t, some of this lubricant will reach the space 84 where it will lubricate the striking surfaces of theharnmerjpin 75 and the anvil extension74. I v

If the hammer pin 75 moves radially outward centrifugally when it is opposite the end of the anvil extension 74, it may strike a rounded corner of the anvil-extension 74 at either cir cumt'erential end of the latter and rebound abruptly back into the recess 76 in the rotor. In such case, the force of such rebound is absorbed by the resilient bumper .87, which prevents breakage of the hammer pin orthe rotor which might otherwise occur under these circumstances.

The spacer '70' maintains the ball bearings 68 and 62 abutting against the respective snap rings 71 'and 63 on the retor. Tll'sjirisures the proper axial positioning of the bearing 62 so that the outer end 82 of the hammer pin will have sufficient clearance to move outward and inwardra'dially. The flat face parted to the anvil 65'from interfering 'with the rotation of the rotort4.

- In accordance with the-present invention, the exhaust passage 77 in the rotor is connected to the atmosphere becomes unseated from the surface 81 on the rotor, and per- I seat member 92. a

v 6 ,.Referring to FIG. 2. the end cap has a cross bore 9] in which a generally cup-shaped valve seat member 92 is tightly seated. A passage 93 formed in end; cap l2 and valve seat 7 member 92' connects the central recess [9 in the endeap to the interior of the valve seat membenfA valve member 94 is disposed in cross bore 9l-for-reciprocation between the normal open position, shown in FIG, 2. inwhich it is retracted away from the valve seat member 92 to permit air to escape to the atmosphere. and the closed position; shown in FIG 5. in which it sealingly engages the valve seat member 92 to block passage 93 from the atmosphere. Valve member 94 has a sufficiently close clearance in bore 91 that it provides a flow restriction between chamber I9 and the atmosphere sufficient to create a back pressure in chamber l9 when air is being 7 discharged from rotor passage 77 past valve member to the atmosphere. I

' Valve member, 94 slidably through the transverse end: wall 96 of valve seat member 92 and is attachedto a gencrallycup-shaped piston- 97. Piston 97 is slidably reciprocable'in bore 91 between the normal position'shown in FIG. 2. in which it is next to the end wall96 of valve seat member'92, and the p'osition'shown in FIG. 3, in which his displaced to the right away from valve At "the right end of cross bore 9!: in FIGS. 2and 3. a fitting 98 is screw"threadedly inserted. This'fittinghas a central passage 99"connecting this e'nd of crossbore 9110 the at-' mospher'e. A coil spring 100 is engaged under compression between fitting 98 and piston 97 to'bias the latter to the lcft as I shown in FIG. 2. I i v The end cap 12 has a large annular recess l0l extending around its central recess 19 and apassageway connecting these two recesses. This passagewaycomprises a passage I02 extending axially from recess 19. a passage IOJ extending axiv ally from-recess I01, and a transverse passage 104 interconnecting passages 102 and 103. An adjustable needle valve 105 is positioned-at the intersection of passages I02 and I04 to control the airflow between them; The annular, recess l0l provides a reservoir for pressurized air which is dischargedthrough the axial passageway 77 in the rotor of the air motor;

ThemeedIe valve 105 provides an adjustable orifice for restricting the flow of pressurized air from passageway 77 into reservoir 101, so that there is a time delay in the buildup of air pressure in reservoir I01 in rcsponse to the discharge of air through the rotor passageway 77. I

The end cap 12 has a screw-threaded recess l06 at its outer I periphery which is closed by a screw-threaded plug 107. The aforementioned transverse passage I04 extends radially outward past the axial passage 103 to the inner end of recess I06. Another transverse passagel08, which is off set both axially and laterally from passage I04, connects the inner end of recess 106 to the middle of the bore 91, as best seen in FIG. 2, immediately to the left of the valve seat member 92. With this arrangement thebore 91 between the valve seat member 92 and the piston 97 is subjected to the air pressure in reservoir I01 by way of the axial passage I03. the outer endof transverse passage 104. the inner end of recess I06 and transverse passage I08 I In operation, the spring I00 normally positions valve member 94 as shown in FIG. 2, so that air discharged from the rotor passageway 77 can pass to theatmosphere through passage 93 and cross bore 91 past valve member 94. As already stated, the clearance between valve member 94 and bore 91 causes a backpressure to be developed in chamber l9, and this back pressure is communicated to reservoir l0] and passage 108 by way of needle valve 105. The flow restricting needle valve 105 delays the buildup of air pressure at through a normally open valve which is arranged to close aupassage 108 each time the hammer pin 75 strikes the anvil 65.

After a predetermined number of blows of the hammer pin 75 against the anvil 65, as determined by the adjustment of needle valve 105 and the volume of reservoir l0], the back pressure at passage 108 will increase to a value effective to move piston 97 to the FIG. 3 position. closing valve member 94 against its seat and preventing the escape of air from rotor isattached to a'stem which extends passageway 77 to the atmosphere. When this happens the back pressure on the hammer pin 75 prevents it from moving inwardly to clear the anvil so that the impact tool stalls completely and remains stalled as long as the user holds the main valve 47 open. The torque load at which the impact tool stalls depends, of course, upon the setting of the needle valve 105. It should be noted that this stalling or release action takes place for either direction of rotation of the air motor. as determined by the position of trigger 38. The stall condition of the impact tool imparts a slight torque to'the users hand due to the rotor rebound. The user may end "the stall condition by releasing the trigger 38 to permit main valve 47 to close, thus turning offthc air motor.

ln operation, during run down, such as when tightening a nut and bolt assembly, the hammer pin 75 remains radially outwardon the rotor, sealingly engaging the valve surface 81, as shown in FIG. 1. At this time there may be some leakage of air through the bearings 18 into the end cap recess 19 and from there through passage 93 and cross bore 91 past valve member 94 to the atmosphere. It will be noted that the tool is particularly adapted for a long run down, with the hammer pin 75 remaining radially outward to impart rotation to the anvil 65 continuously throughout the run down.

When the tool is used to draw down a spring or a soft load, such as sheet metal parts, light impacting takes place with little rebounding of the rotor so that any unloading of the air pressure in chamber 84 due to inward movement of the hammer pin 75 is not enough to cause the piston 97 to move to the valve-closing position.

However, when the tool encounters a predetermined heavy load, the resulting heavy rebound causes the hammer pin 75 to move inward sufficiently to cause piston movement to the valve-closing position, as described.

While a presently preferred embodiment of this invention ha'sbeen disclosed with reference to the accompanying drawing, it is to be understood that various modifications, omislclaim: 1. In a rotary impact tool having a housing, a rotary air 1 motor in said housing, said housing having a chamber therein which is exposed to air pressure from said motor, said air motor having a rotor with a passage therein, said rotor extending into said housing chamber, a rotatable anvil having an extension disposed within said housing chamber, said rotor havinga laterally disposed recess therein which is open to said rotor passage and whose outer end opens into said chamber, a hammer pin slidably mounted in said recess for centrifugal movement laterally outward into said chamber to strike said anvil extension an impact blow for imparting rotation from the rotor to the anvil and for retraction inwardly to disengage from said anvil. the improvement which comprises means controlling the venting of the inner end of said recess through said rotor passage to the atmosphere to provide sufficient back pressure on the inner end of said hammer pin to prevent its inward retraction at a predetermined torque load on said anvil.

2. An impact tool according to claim 1, wherein said lastmentioned means is adjustable to selectively determine the torque load at which the inward retraction of the hammer pin is prevented.

3v An impact tool according to claim 1, wherein said lastmentioned means comprises a normally open valve venting said rotor passage to the atmosphere, and movable pressure responsive means for closing said valve to block said rotor passage from the atmosphere.

4. An impact tool according to claim 3, and further comprising passage means connecting said rotor passage to said 5. An impact tool according to claim 4, wherein said means providing said flow restriction is adjustable to selectively vary the torque load at which the inward retraction ofthe hammer pin is preventedv 6. An impact tool according to claim 4, and further-comprising means providing an airireservoir communicating-,with said movable pressure responsivemeans ;after-said i'tlow restriction to delay the buildup of the a'ir'pressi'ire acting on said movable pressure responsivemeans.

7. An impact tool according to'claim 4, wherein said valve when open has means which partially restricts the venting of air to the atmosphere and causes back pressure at saidpassage means ahead of said means providing the flow restriction therein.

8. An impact tool according to claim 7, wherein said means providing the flow restriction is adjustable. to selectively vary the torque load at which the inward retraction of the hammer pin is prevented.

9. An impact tool according to claim' 8, and further comprising means providing an air reservoir communicating with said movable pressure responsive means after said flow restriction to delay the buildup of the air pressure acting on said movable pressure responsive means.

10. An impact tool according to claim I, wherein said air motor is reversible and'has an air inlet, and further comprising directional valve means connected to the motor inlet to control the latter's direction of operation, means biasing" said directional valve means to a position for establishing operation of the motor in one direction, an on-off valve connected to said directional valve means and "the motor inlet to control the flow of air into the motor, means biasing said -on-off valve to a closed position blocking the air flow to said motor inlet, main trigger means for opening said on-off valve to pass an to said motor inlet, and reversing trigger means movable to cause said on-off valve to open and also to move said directional valve means to a position for establishing operation of the motor in the opposite direction, and wherein said means controlling the venting of said recess is operable to prevent the inward retraction of the hammer pin at a predetermined load in either direction of operation of the air motor.

11. A rotary impact tool comprising a housing, a rotary air motor in said housing, said housing having a chamber therein which is exposed to air pressure from said motor, said motor having a rotor with a passage therein, a rotatable anvil having an extension disposed within said housing chamber, said rotor having a laterally disposed recess therein which is operito said rotor passage and whose outer end opens into said chamber, a hammer pin slidably mounted in said recess for centrifugal movement laterally outward into said chamber to strike said anvil extension an impact blow for imparting rotation from the rotor to the anvil, said hammer pin sealingly engaging the rotor at said laterally disposed recess therein to block said chamber from said rotor passage when the hammer pin is laterally outward on the rotor, said hammer pin when retracted laterally inward into said recess connecting said chamber to said rotor passage, an end cap on said housing having passage means communicating with said rotor passage, and means at said passage means for controlling the venting of said rotor passage to the atmosphere to provide sufficient back pressure on the inner end of the hammer pin to prevent its inward retraction at a predetermined torque load on the anvil. i

12. An impact tool according to claim 11 wherein said lastmentioned means comprises a normally open valve bending said rotor passage to the atmosphere and partially restricting said venting, and movable pressure responsive means for closing said valve, said movable pressure responsive means being exposed to said passage means in the end cap.

13. An impact tool according to claim 12, wherein said passage means in the end cap includes a bore which is open to the atmosphere, said normally open valve comprises a valve seat member positioned in said bore and providing a valve seat, and a valve member reciprocable in said bore toward and away from said valve seat aimaving a sufficiently close clearance in said bore to partiallyrestrict the venting of air through said bore to the atmosphere, and wherein said passage means in the end cap includes means connecting the rotor passage to said bore at one side of said valve seat, and said movable pressure responsive means comprises a pistonslida ble in said bore and connected to said valve member, and further comprising spring means biasing said piston to a position in which said valve member is unseated from said valve seat.

14. An impact tool according to claim 12, and further comprising means providing a flow restriction in said passage means in the end cap to delay the buildup of air pressure acting on said movable pressure responsive means.

15. An impact tool according to claim 14, wherein said means providing the flow restriction is adjustable.

16. An impact tool according to claim 15, wherein said means for controlling the venting of said rotor passage com prises an air reservoir in said end cap communicating with said movable pressure responsive means after the flow restriction.

17. An impact tool according to claim 16, wherein said passage means in the end cap includes a bore which is open at each end, and said normally open valve comprises a valve seat member positioned in said bore and presenting a valve seat at one end thereof, and a movable valve member in said bore engageable with said valve seat, said passage means in the end cap includes a passage leading to said valve seat at the opposite side of the latter from said movable valve member, said movable valve member having a sufficiently close clearance in said bore to partially restrict the venting of air to the atmosphere through said bore when said valve member is unseated from said valve seat, said passage means in the end cap includes another passage communicating with said reservoir and intersecting said bore at the opposite end of the valve seat member from the latters valve seat. and said movable pressure responsive means is a piston slidable in said-bore at said opposite end of the valve seat member and connected rigidly to said movable valve member, and further comprising a spring biasing said piston toward said opposite end of the valve seat member to position said movable valve member away from said valve seat.

18. An impact tool according to claim 17. wherein said air motor is reversible and has an air inlet, and further comprising directional valve means connected to the motor inlet to control the latter's direction of operation, means biasing said directional valve means to a position for establishing rotation of the motor in one direction, an on-off valve connected to said directional valve means and the motor inlet to control the flow of air into the motor, means biasing said on-off valve to a closed position blocking the air flow to said motor inlet, main trigger means for opening said on-off valve to pass fluid to said motor inlet, and reversing trigger means movable to cause said on-off valve to open and also to move said directional valve means to a position for establishing rotation of the motor in the opposite direction.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,556,230 Dated January I9, 1971 Inventor) Earl G. Romg nburk It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 46, "then" should be -fhin--. Coiumn 8, line 66, "bending" should be venring.

Signed and sealed this 25th day of May 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SGHU'XLER, JR. attesting Officer Commissioner of Patents 

1. In a rotary impact tool having a housing, a rotary air motor in said housing, said housing having a chamber therein which is exposed to air pressure from said motor, said air motor having a rotor with a passage therein, said rotor extending into said housing chamber, a rotatable anvil having an extension disposed within said housing chamber, said rotor having a laterally disposed recess therein which is open to said rotor passage and whose outer end opens into said chamber, a hammer pin slidably mounted in said recess for centrifugal movement laterally outward into said chamber to strike said anvil extension an impact blow for imparting rotation from the rotor to the anvil and for retraction inwardly to disengage from said anvil, the improvement which comprises means controlling the venting of the inner end of said recess through said rotor passage to the atmosphere to provide sufficient back pressure on the inner end of said hammer pin to prevent its inward retraction at a predetermined torque load on said anvil.
 2. An impact tool according to claim 1, wherein said last-mentioned means is adjustable to selectively determine the torque load at which the inward retraction of the hammer pin is prevented.
 3. An impact tool according to claim 1, wherein said last-mentioned means comprises a normally open valve venting said rotor passage to the atmosphere, and movable pressure responsive means for closing said valve to block said rotor passage from the atmosphere.
 4. An impact tool according to claim 3, and further comprising passage means connecting said rotor passage to said movable pressure responsive means, and means providing a flow restriction in said passage means to delay the buildup of the air pressure acting on said movable pressure responsive means for closing said valve.
 5. An impact tool according to claim 4, wherein said means providing said flow restriction is adjustable to selectively vary the torque load at which the inward retraction of the hammer pin is prevented.
 6. An impact tool according to claim 4, and further comprising means providing an air reservoir communicating with said movable pressure responsive means after said flow restriction to delay the buildup of the air pressure acting on said movable pressure responsive means.
 7. An impact tool according to claim 4, wherein said valve when open has means which partially restricts the venting of air to the atmosphere and causes back pressure at said passage means ahead of said means providing the flow restriction therein.
 8. An impact tool according to claim 7, wherein said means providing the flow restriction is adjustable to selectively vary the torque load at which the inward retraction of the hammer pin is prevented.
 9. An impact tool according to claim 8, and further comprising means providing an air reservoir communicating with said movable pressure responsive means after said flow restriction to delay the buildup of the air pressure acting on said movable pressure responsive means.
 10. An impact tool according to claim 1, wherein said air motor is reversible and has an air inlet, and further comprising directional valve means connected to the motor inlet to control the latter''s direction of operation, means biasing said directional valve means to a position for establishing operation of the motor in one direction, an on-off valve connected to said directional valve means and the motor inlet to control the flow of air into the motor, means biasing said on-off valve to a closed position Blocking the air flow to said motor inlet, main trigger means for opening said on-off valve to pass air to said motor inlet, and reversing trigger means movable to cause said on-off valve to open and also to move said directional valve means to a position for establishing operation of the motor in the opposite direction, and wherein said means controlling the venting of said recess is operable to prevent the inward retraction of the hammer pin at a predetermined load in either direction of operation of the air motor.
 11. A rotary impact tool comprising a housing, a rotary air motor in said housing, said housing having a chamber therein which is exposed to air pressure from said motor, said motor having a rotor with a passage therein, a rotatable anvil having an extension disposed within said housing chamber, said rotor having a laterally disposed recess therein which is open to said rotor passage and whose outer end opens into said chamber, a hammer pin slidably mounted in said recess for centrifugal movement laterally outward into said chamber to strike said anvil extension an impact blow for imparting rotation from the rotor to the anvil, said hammer pin sealingly engaging the rotor at said laterally disposed recess therein to block said chamber from said rotor passage when the hammer pin is laterally outward on the rotor, said hammer pin when retracted laterally inward into said recess connecting said chamber to said rotor passage, an end cap on said housing having passage means communicating with said rotor passage, and means at said passage means for controlling the venting of said rotor passage to the atmosphere to provide sufficient back pressure on the inner end of the hammer pin to prevent its inward retraction at a predetermined torque load on the anvil.
 12. An impact tool according to claim 11 wherein said last-mentioned means comprises a normally open valve bending said rotor passage to the atmosphere and partially restricting said venting, and movable pressure responsive means for closing said valve, said movable pressure responsive means being exposed to said passage means in the end cap.
 13. An impact tool according to claim 12, wherein said passage means in the end cap includes a bore which is open to the atmosphere, said normally open valve comprises a valve seat member positioned in said bore and providing a valve seat, and a valve member reciprocable in said bore toward and away from said valve seat and having a sufficiently close clearance in said bore to partially restrict the venting of air through said bore to the atmosphere, and wherein said passage means in the end cap includes means connecting the rotor passage to said bore at one side of said valve seat, and said movable pressure responsive means comprises a piston slidable in said bore and connected to said valve member, and further comprising spring means biasing said piston to a position in which said valve member is unseated from said valve seat.
 14. An impact tool according to claim 12, and further comprising means providing a flow restriction in said passage means in the end cap to delay the buildup of air pressure acting on said movable pressure responsive means.
 15. An impact tool according to claim 14, wherein said means providing the flow restriction is adjustable.
 16. An impact tool according to claim 15, wherein said means for controlling the venting of said rotor passage comprises an air reservoir in said end cap communicating with said movable pressure responsive means after the flow restriction.
 17. An impact tool according to claim 16, wherein said passage means in the end cap includes a bore which is open at each end, and said normally open valve comprises a valve seat member positioned in said bore and presenting a valve seat at one end thereof, and a movable valve member in said bore engageable with said valve seat, said passage means in the end cap includes a passage leading to said valve seat at the opposite side of the latter from said movable valve member, said movable valve member having a sufficiently close clearance in said bore to partially restrict the venting of air to the atmosphere through said bore when said valve member is unseated from said valve seat, said passage means in the end cap includes another passage communicating with said reservoir and intersecting said bore at the opposite end of the valve seat member from the latter''s valve seat, and said movable pressure responsive means is a piston slidable in said bore at said opposite end of the valve seat member and connected rigidly to said movable valve member, and further comprising a spring biasing said piston toward said opposite end of the valve seat member to position said movable valve member away from said valve seat.
 18. An impact tool according to claim 17, wherein said air motor is reversible and has an air inlet, and further comprising directional valve means connected to the motor inlet to control the latter''s direction of operation, means biasing said directional valve means to a position for establishing rotation of the motor in one direction, an on-off valve connected to said directional valve means and the motor inlet to control the flow of air into the motor, means biasing said on-off valve to a closed position blocking the air flow to said motor inlet, main trigger means for opening said on-off valve to pass fluid to said motor inlet, and reversing trigger means movable to cause said on-off valve to open and also to move said directional valve means to a position for establishing rotation of the motor in the opposite direction. 